I would have thought you could have any icing you like. Funnily enough, I`m going to make a carrot cake this afternoon. I usually sprinkle a bit of orange or lemon zest over the top. That might work if the butter icing is a bit rich.
I don't think butter icing will do, and even if you try It won't taste as yummy as cheese cream. If you can't get cheese cream then I will recommend you to buy Carrot Cake from "Deliciae", their cake is just awesome in taste.